With the growth of the electric vehicle (EV) industry, infrastructure is constantly being added to enable “opportunity” charging, e.g., charging in public spaces such as at parking lots in shopping centers, in city centers, and at work places. The charging infrastructure involves at least two aspects: the installation of electric vehicle supply equipment (EVSEs), and the installation of a power system (e.g., a power distribution infrastructure) to supply power to the EVSEs. An EVSE, also referred to as a charging station or an EV charging station (EVCS), supplies power from the power system to an EV in order to charge the EV's battery.
Two distinct varieties of commercial EVSEs are available: AC charging stations and DC charging stations. DC EVSEs are typically “fast charge” stations which require large amounts of power (e.g., 50 kW or more), and are typically provided by 3-phase power systems. They are the larger and more expensive variety of charging stations because they incorporate power electronics required for providing variable voltage and current as requested by the EV. AC charging stations, however, only require connection to a single phase power supply which is readily available, and are significantly less expensive as they incorporate no power electronics to condition the power provided to the EV. Based on the lower cost to own and operate, the AC charger is more common for opportunity charging applications.
As an EVSE represents a substantial load to the power system, the installation of EVSEs requires specific power system consideration. For example, local electrical codes specify requirements for connecting an EVSE to a power system. In the United States, the National Electric Code (NEC) specifies the required capacity of the power system for EVSEs. As specified by the NEC, the service providing power to an EVSE must be capable of providing power for all downstream EVSEs at maximum load simultaneously, unless an energy management system is used. For most installations, the average load from one or more EVSEs is significantly lower than the maximum load. Thus, an energy management system can be used to downsize service for an installation of EVSEs, and thus, to reduce the overall cost of installing and operating a charging infrastructure.
Traditional energy management systems, however, require the use of a central controller, and a means of addressing and querying individual EVSEs to monitor and control the charging rate at each EVSE. Systems designed around a central controller have inherent characteristics that must be addressed. For example, the central controller must be able to communicate with every EVSE individually, which adds complexity to the installation in terms of materials and labor, and complexity to the design of both the controller and the EVSEs. Further, traditional energy management systems cannot be easily updated with additional EVSEs or capabilities, or easily accommodate changes in the available capacity or variable target capacity utilization. For example, the central controller and the EVSE may need to be re-programmed or re-designed to incorporate new capabilities, to add or remove EVSEs in the system, or to address compatibility issues when updating the system.